Technology: Program puts the right angle on TV dishes

日期:2019-02-28 09:03:01 作者:戈邰 阅读:

YOUNG chemistry graduate from Bath University has come up with a computer program that will help anyone who installs a dish aerial to point it accurately at the correct satellite. The program, developed by Robert Breeds, performs the complex calculations that are necessary to locate satellites for any receiver in Europe. For Pounds sterling 3 he will provide a printout listing the exact azimuth and elevation angles for each of the 30 satellites serving Europe from any location of dish. To receive signals, a dish aerial must be aligned to an accuracy of 1 degree, horizontally and vertically. Although information on the orbital positions allocated to all satellites is freely available, the azimuth and elevation angles vary considerably for each location. The elevation angle reduces as the receiver site moves north, further away from the equator over which all geostationary satellites hang at a height of 36 000 kilometres. At the same time, the azimuth angle changes as the receiver site moves to either side of the Greenwich meridian. The orbital angle is only accurate for the North Pole. So an aerial in London aimed at Astra, whose azimuthal angle is at 19.2Degree East, will have to point at 24.1Degree East instead. Accurate information is even more important if the dish is pivoted on a polar mount so that a motor drive can move it across the sky to ‘see’ more than one satellite, like a telescope tracking the stars. Satellites in geostationary orbit are far closer than the stars, and complex controls are needed to keep the dish in line with satellites spread across the horizon. Breeds wrote a computer program to do all the necessary calculations for fixed and polar mounts. Initially, it was for his own use. Now, with the help of Swift Television Publications of Cricklade near Swindon in Wiltshire,